Cells obtained by filtration leucapheresis using current methods were demonstrated by SEM, TEM, cyto-chemical and functional testing to be altered during harvesting and processing for transfusion. In a model system, we demonstrated that washing harvested cells in HBSS and brief incubation in heparinized autologous plasma significantly restored them structurally and functionally. Preliminary clinical trials of this method have been made and results are encouraging. In a case submitted for our study, we demonstrated the accepted micromorphological criteria for Hairy Cell Leukemia, mononuclear clear cells with numerous cytoplasmic projections at the periphery. Zipper-like junctions were demonstrated in these cells as well as their ability to phagocytose microorganisms. These are properties of cells of the monocytic series, and strongly suggest the non-lymphoid origin of Hairy Cells. We will continue our investigation of methods to restore to maximal viability and efficiency, granulocytes collected for transfusion therapy. Cytochemical study of the glycocalyx of leukemic cells and utilization of SEM and TEM to elucidate the zipperlike junctions in leukemic monocytes and Hairy Cell Leukemias will be pursued.